LED Light for 36" High Tank - Page 11 - The Planted Tank Forum
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post #151 of 269 (permalink) Old 06-16-2011, 02:38 PM
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So much for sunrise & sunset simulations with Meanwell drivers. Oh I guess they meant well

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post #152 of 269 (permalink) Old 06-16-2011, 03:03 PM Thread Starter
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Quote:
Originally Posted by cggorman View Post
That's a limitation of the Meanwell driver. They clip below 15%...much to my dismay.

As you've discovered, 15% brightness on these lighting-class diodes is still really bright.
The rated current for the driver is 700 mAmps, or that is the current at which they give the lumen output, and the point on the lumens vs current curve called 100%. 15% of 1300 mA is about 200 mA, and I can't keep them going below about 400 mA. Something else must be happening.

I knew these LEDs are very bright, but I relied on the data in the Cree pdf which shows lumens vs LED current, and which goes down to less than 200 mAmps. I have to believe that Cree isn't fudging data, so there must be something else happening.

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Originally Posted by redfishsc View Post
I doubt it. The drivers are designed to automatically compensate for voltage drop as current drops.

Is this happening on the XPEs as well, and happening consistently on the two different XML strings?
The XPE's are on a fixed 350 mA driver, so they aren't affected. When I had a similar problem with my last LED light, which had closer to the maximum number of LEDs on the driver, I just adjusted the pot in the driver to a higher voltage output, and the problem went away. This light is acting like the other one - the LEDs light for a few seconds, then go off until I increase the current to them. It won't cost anything to try adjusting the voltage, so I plan to do that just in case it helps.

I'm going to be away from Saturday thru next Thursday, so it may be awhile before I get time to play with this.

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post #153 of 269 (permalink) Old 06-16-2011, 03:14 PM
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Try bypassing a couple of LEDs with a shunt wire and see how it behaves with less LEDs in series.

Steve

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post #154 of 269 (permalink) Old 06-16-2011, 03:48 PM
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200mA at what Vf and what voltage is the driver supplying? I can't honestly see that being the problem since the voltage trim pot is a limiter and the Vf @ 200mA can't be much, but who knows....

My ELN-60-48P shipped putting out 1.4A@ 56v. (Way over the rated max for both). I dialed it back to 1.2A but left the voltage at maximum since the driver actively manages it.

I've gotta say that so far I'm not terribly impressed with the Meanwells. Wondering if I should have gone with the Magtechs or Maxims
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post #155 of 269 (permalink) Old 06-16-2011, 04:34 PM Thread Starter
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Suppose I were to adjust the drivers down to 800 mAmps maximum. Would that also reduce the minimum current output proportionally? Of course if the problem is that the LEDs can't operate at low currents it wouldn't help.

I considered shunting out a LED, but I hate to tamper with it that way. That would certainly eliminate available voltage as a problem.

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post #156 of 269 (permalink) Old 06-16-2011, 04:52 PM
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I believe it does, yes. When I was tinkering with mine, I believe I could get a lower minimum brightess as I turned down the current trimmer. In my case, it sacrificed too much at the high end, but it sounds like that's ok for you.
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post #157 of 269 (permalink) Old 06-16-2011, 05:07 PM Thread Starter
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I believe it does, yes. When I was tinkering with mine, I believe I could get a lower minimum brightess as I turned down the current trimmer. In my case, it sacrificed too much at the high end, but it sounds like that's ok for you.
That looks like the best bet for now. If I didn't have to get ready for the trip I'm going on I could try it right away. I need to set up the light with a PAR meter to do this well, and there are just too many other odd jobs to do first.

I really appreciate the help I'm getting from you guys. Without this forum I wouldn't dare try a DIY project like this.

Hoppy
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post #158 of 269 (permalink) Old 06-16-2011, 05:31 PM
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I wonder if the PWM Meanwells have this issue?

Steve

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post #159 of 269 (permalink) Old 06-16-2011, 06:53 PM
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I get the same results across all the following:

ELN-60-48P driving twelve 5W LEDs
ELN-30-27D driving six 5W LEDs
ELN-30-48D driving six 3W LEDs

During my testing phase, I was using resistors and pots to dial back a 200W computer power supply (dialing back a 5V leg to drive single LEDs) and I could dim them smoothly all the way to black (off).

Here is a copy of the Meanwell ELN series dimming graphs (from their published PDF) Looks like the Ds (that's what Hoppy is using, I believe) clip at 5%

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post #160 of 269 (permalink) Old 06-16-2011, 07:36 PM
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Suppose I were to adjust the drivers down to 800 mAmps maximum. Would that also reduce the minimum current output proportionally? Of course if the problem is that the LEDs can't operate at low currents it wouldn't help.


I think you are right, Hoppy. I seem to recall having the driver cranked up to 1450mA for my XPGs once and they wouldn't dim all the way off, but if set at 990mA, they do dim all the way off if I drop the reference voltage.
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post #161 of 269 (permalink) Old 06-16-2011, 09:22 PM Thread Starter
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I'm very encouraged! When I get back to this I should be able to make it work. And, my drivers may be set at more than 1300 mA, since I have no convenient way to measure it, with the digital ammeters not working for me. And, I have no way of knowing what the current is since my digital ammeters don't work. I should be able to use the PAR meter to get to a good adjustment by interation - adjust, try to dim, readjust, try to dim, etc.

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post #162 of 269 (permalink) Old 06-17-2011, 03:00 AM
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Well the nice thing about the XM-Ls is that you can't blow 'em with that Meanwell no matter what you set them at.

Steve

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post #163 of 269 (permalink) Old 06-17-2011, 03:38 AM
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I'm very encouraged! When I get back to this I should be able to make it work. And, my drivers may be set at more than 1300 mA, since I have no convenient way to measure it, with the digital ammeters not working for me. And, I have no way of knowing what the current is since my digital ammeters don't work. I should be able to use the PAR meter to get to a good adjustment by interation - adjust, try to dim, readjust, try to dim, etc.
They may well be sitting at way higher, depending on how they came set from the factory. The ELN models can, sometimes, vary wildly. I've heard of them (from a retailer that stopped carrying them) showing up giving 1.5A and 700mA, varying one from the next.

I haven't ever tested the "out of the box" amperage, I always turn it all the way down first, hook up the multimeter, and adjust it running. Works like a charm.


I just finished my stand and canopy (stain/clearcoat) for my tank yesterday, and it's ready to install.............. gonna be a fun weekend .
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post #164 of 269 (permalink) Old 06-17-2011, 04:28 AM
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So i copied hoppy's wiring except i put my ammeter in series on the negative terminal of my LED lights instead of the positive side and everything works perfectly. I didn't have to change the max current on my Mean Well ELN-60-48D dimmable driver and I can get the lights to run from about .15 A to 1.4 A (according to my ammeter). I think you just got a bad ammeter. I have the exact same model that you got with pretty much identical wiring and it is working perfectly.

you can check out my LED build thread to see the finished project. All the wires are inside of the plastic box but the wiring is identical to hoppy's.
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post #165 of 269 (permalink) Old 06-17-2011, 02:55 PM Thread Starter
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I just got a month's reprieve on when the light is needed, so I may go back to trying to get the ammeters to work for me, too. Putting them on the negative side may be important - the instructions show it wired that way. For the next week, though, I will be away - in Georgia, in fact.

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